1. Field of the Invention
This invention pertains to methods and apparatus for vacuum forming an elastomeric transport tire containing a core of belts, plies and beads.
2. Prior Art
The present invention is in a new and unique vacuum forming apparatus for use in an automated method for forming a transport tire from an elastomeric material that includes a core of optimally positioned belts, plies and beads, to provide a balanced transport tire.
Heretofore it was recognized that venting air from a tire tread mold cavity early in a casting process could eliminate the necessity for venting the cavity through spaced holes in the mold that materials from the tread flowed into during casting and formed projections or “tits”. Such extensions or ‘tits’ projected from the tread surface and were either pulled off when the tire was removed from the mold, had to be cut off or wore off during tire use. To prevent this undesirable cosmetic anomaly it was recognized that air could be vented from the mold cavity just before tread casting, eliminating a necessity for providing flow passages or vents from the tire tread mold while still obtaining a smooth, un-pocketed or un-blemished, finished tread surface. Examples of such an introduction of a vacuum into a tire mold just prior to forming a tire tread are shown in U.S. Pat. Nos. 4,573,894 and 5,152,951.
U.S. Pat. No. 4,573,394 sets out a tire mold having a cavity that is for receiving and finally shaping the tire. The patent is defined by a surface that is for contacting the exterior of the tire during tire curing. The cavity is fluid connected to a single vacuum source for evacuating air from within the cavity during an early portion of a tire curing cycle to prevent air and any other fluid from becoming trapped between the tire and the surface that defines the cavity that will become the tire tread. Visual effects in the form of voids in the tire exterior are, thus eliminated.
Like the '894 patent, U.S. Pat. No. 5,152,951 also provides for the elimination of fluid from the mold cavity during an early portion of a tire curing cycle. The patent provides for fluid evacuation through a space between the surfaces of the mold parts that defines the mold parting line region. Both patents provide a single vacuum source and its connection to the mold cavity for forming the tire side wall and tread surfaces. Whereas, the present invention provides for both an evacuation of air from the elastomeric mixture prior to its introduction into the mold cavity, and for pulling the air free mixture through the mold. With that flow filling the area between inner and outer mold walls, traveling through the core of plies, belts and beads, to form a finished transport tire that is free of voids or pockets.
A core of plies, belts and beads for use in the vacuum forming apparatus of the invention is set out in a U.S. patent application for a “Tire Core Package for Use in Manufacturing a Tire With Belts, Plies and Beads and Process of Tire Manufacture” Ser. No. 10/143,678, filed May 13, 2002, of two of the inventor, and is presently pending. This patent application sets out a process, utilizing a sandwich of pre-cured elastomer layers between layers of plies and belts formed over a mandrel for fitting into a mold, for forming a tire utilizing a spin casting method. Also, one of the inventors of the present application is the sole inventor of a U.S. patent application for an “Elastomeric Tire With Arch Shaped Shoulders” filed May 28, 2004, assigned Ser. No. 10/856,652.
The present invention is a new approach to forming a transport tire from an elastomeric material from earlier patent applications for spin casting apparatus and methods for use in such spin casting apparatus for forming a transport tire that are shown and discussed in a recently filed U.S. patent applications of two of the inventors, entitled, “Method and Apparatus for Forming a Core of Plies, Belts and Beads and For Positioning the Core in a Mold For Forming an Elastomeric Tire and the Formed Elastomeric Tire”, filed Jun. 4, 2004, Assigned Ser. No. 10/860,997, and an “Improved Method and Apparatus for Forming a Core of Plies, Belts and Beads and for Positioning the Core in a Mold for Forming an Elastomeric Tire”, filed Aug. 2, 2004, assigned Ser. No. 10/809/807. All of which earlier patents are directed to spin casting methods and apparatus and do not involve a vacuum forming apparatus and method as does the present invention.